确定没有打错题目吗?题目中的a是什么?答案中又怎么没有a?
则：（x^2+5x+4）/(x^4+5x^2+4)=(x^2+5x+4)/(x^2+1)(x^2+4)
=1/(x^2+1)+5x/(x^2+1)(x^2+4)
∫(x^2+5x+4)dx/(x^4+5x^2+a)=∫dx/(x^2+1)+∫5x/(x^2+1)(x^2+4)dx
而∫dx/(x^2+1)=arctanx
∫5x/(x^2+1)(x^2+4)dx=5/2∫d(x^2)/(x^2+1)(x^2+4)
=5/6∫[1/(x^2+1)-1/(x^2+4)]d(x^2)
=5/6[ln(x^2+1)-ln(x^2+4)]
=5/6*ln[(x^2+1)/(x^2+4)]
故∫(x^2+5x+4)dx/(x^4+5x^2+a)
=5/6ln[(x^2+1)/(x^2+4)]+arctanx+c